Constant-flow device

Abstract

The invention relates to a constant-flow device. A logic control unit controls a first power tube to be conducted, a primary winding of a first transformer starts to store energy, a first comparator generates a signal for switching off the first power tube, and the energy stored by the first transformer is released by a secondary winding; according to a relation of a same phase of an auxiliary winding and the secondary winding, the demagnetization duty ratio of the auxiliary winding can be obtained, and a demagnetization duty ratio detection unit transmits a demagnetization duty ratio signal to a current gating unit and controls switching-on and switching-off of the current gating unit; a reference current unit is a pull-down current source and always discharges for a first capacitor, andwhen dynamic balance is achieved, the average current which flows in the current gating unit is equal to the pull-down current of the reference current unit. According to the constant-flow device, theoutput current is only related to the reference current of the reference current unit, constant-flow output is achieved during output of different voltages, any sampling resistor does not need to bearranged at the secondary side of the transformer, the outer space and cost are saved, and the whole efficiency is improved.

Description

technical field [0001] The invention relates to the field of switching power supplies, in particular to a constant current device. Background technique [0002] With the rapid popularization of large-screen smartphones, the requirements for battery capacity are getting higher and higher, and the corresponding charging speed is also required to be faster and faster. Now the typical fast charging field is QC3.0, QC4.0; QC4.0 The charging power reaches nearly 30W, and the output current of the five-volt output gear can reach 6A. The current most popular QC3.0 and QC4.0 charging circuits mostly use the constant current on the secondary side of the transformer, and set the constant current sampling resistor. The sampling resistor must be at least 10mΩ, and the loss of at least 0.36W on the sampling resistor will reduce the efficiency of the entire system by 1.5%. Contents of the invention [0003] The technical problem to be solved by the present invention is to provide a cons...

AI Technical Summary

Problems solved by technology

[0002] With the rapid popularization of large-screen smartphones, the requirements for battery capacity are getting higher and higher, and the corresponding charging speed is also required to be faster and faster. Now the typical fast charging field is QC3.0, QC4.0; QC4.0 The charging power reaches nearly 30W, and the output current of the five-volt output gear can reach 6A. The current most popular QC3.0 and QC4.0 charging circuits mostly use the constant current on the secondary side of the transformer, and set the constant current sampling resistor. The sampling resistor must be at least 10mΩ, and the loss of at least 0.36W on the sampling resistor will reduce the efficiency of the entire system by 1.5%.

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